This invention relates to a sheet feeding apparatus for feeding sheets seriatum from a stack of sheets. More particularly, this invention relates to a sheet feeding apparatus for delivering a sheet in a desired configuration to a position remote from the stack of sheets.
Prior to the present invention, document feeders have been available for transporting document sheets one by one from a stack of document sheets to an area remote from the stack. Such apparatus are use, for example in xerographic copying machines or labeling machines. It is necessary that the document sheets be transported seriatum, one at a time, in order to avoid machine jamming or misorientation of the document sheet at the delivered area remote from the stack.
It has been proposed in U.S. Pat. No. 3,815,900 to provide a document sheet feed apparatus utilizing a driven roller which contacts the top sheet of a stack of document sheets when it is desired, to remove the top sheet from the stack and is out of contact with the stack within the time period when successive sheets are removed from the stack. Contact and non-contact of the driven roller with the stack is controlled by means of a cam-cam follower arrangement. This arrangement dictates that the vertical height of the driven roller relative to the sheet stack is controlled solely by the cam surface configuration. This is undesirable since this arrangement does not account for variations in the stack height which change the stack position relative to the driven roller. The results in variation is friction force on successive top sheets which results in non-uniform sheet movement.
U.S. Pat. No. 4,395,032 discloses an apparatus for feeding document sheets one by one from a stack of sheets. The apparatus utilizes two drive belts controlled by a single motor. The driving belts are mounted in a fixed position relative to each other within a frame. The arrangement is undesirable since the drive belts cannot be moved independently to contact the top sheet of a document sheet stack. Since, oftentimes the top sheet surface is not entirely level, the friction forces exerted by each of the two belts on the top sheet differs from each other. This results in the document being skewed away from its desired position. In addition, the feeder cannot be used with varying size documents since the space between the driver belt is fixed.
Accordingly, it would be desirable to provide document sheet feeding apparatus which is efficient in reproducibly positioning documents in a desired position and configuration and which is flexible in accommodating a variety of document sheet sizes.